Synergistic flame-retardant compositions



United States Patent 3,530,089 SYNERGISTIC FLAME-RETARDANT COMPOSITIONSChristos Savides, Piscataway Township, Middlesex County, N.J., assignorto American Cyanamid Company, Stamford, Conn, a corporation of Maine N0Drawing. Filed July 1, 1968, Ser. No. 741,251) Int. Cl. C(lSf 45/58,45/60; (108g 51/60 US. Cl. 260-45.8 Claims ABSTRACT OF THE DISCLOSURESynergistic flame-retardant compositions comprising a monophosphoniumhalide and 2,3 dicarboxy-S,8-endomethylene 5,6,7,8,9,9 hexachlorol,2,3,4,4a,5,8,8a octahydronaphthalene anhydride and its esters andcompositions comprising a thermoplastic resin and said synergisticcompositions are disclosed.

BACKGROUND OF THE INVENTION The production of thermoplastic resincompositions which are flame-retardant is of considerable commercialimportance in that such articles as castings, moldings, foamed orlaminated articles. etc. are required, or at least desired, to beresistant to fire and flame and to possess the ability to endure heatwithout deterioration. Typical illustrations of applications of suchcompositions include castings for live electrical contacts which shouldnot be ignited by 'fiame or sparks, structural members such as pipes,wall coverings, wall paneling, windows, etc. and such items as ashtrays, waste baskets, fibers and the like.

The use of certain additives for the purpose of reducing theflammability of various thermoplastic polymers is well known to thoseskilled in the art. Among the additives currently employed for such ause are various specific types of phosphorus-containing compounds. Thesephosphorus compounds are generally used either alone or in combinationwith other materials such as aliphatic or aromatic antimonous compounds.Certain analogous materials such as chlorostyrene copolymers,chlorinated parafiin waxes, alone or with antimony oxide or phosphoruscompounds are also known to effective flame-retardants for resinousmaterials. One drawback of many of these known compounds andcombinations of compounds, however, has been the fact that generallylarge amounts, i.e., upwards of 45%, of the additive must beincorporated into the polymer in order to render it reasonablyflame-retardant. Such large quantities of additive oftimes deleteriouslyalter the properties of the polymer and moreover, some additives tend tocrystallize or oil out of the polymer after a relatively short time orincorporation therein.

Furthermore, these prior art systems generally are thermally unstableand, as such, are not suitable for incorporation into polymericmaterials Which require high temperature processing conditions becausethey tend to discolor or otherwise degrade the resultant processedpolymer rendering it unfit for ultimate commercial applications.Additionally, most of the prior art additives are liquid in theirnatural or most common state and therefore may affect other physicalproperties of the polymeric material to which they are added.

SUMMARY I have now found that superior flame-retarding properties can beimparted to thermoplastic polymers by in- Ice corporating into thepolymer a synergistic combination or mixture of (A) a compound havingthe formula wherein R and R taken together constitute an oxygen atom orR and R taken separately are, individually, a hydroxy radical, an alkoxyradical of l8 carbon atoms, inclusive, or a haloalkoxy radical of l4carbon atoms, inclusive and (B) a monophosphonium halide having theformula wherein R R R and R are, individually, hydrogen, an alkylradical of l8 carbon atoms, inclusive, a cyano, hydroxy, or carboxysubstituted alkyl radical of 1-4 carbon atoms, inclusive, an allylradical, an aryl radical of 6-10 carbon atoms, inclusive, an aralkylradical of 7-.l1 carbon atoms, inclusive, a halo or polyhaloar-substituted aralkyl radical of 7-11 carbon atoms, inclusive, or acarboalkoxyalkyl radical of 3-6 carbon atoms, inclusive, and Xrepresents chlorine or bromine, no more than one of R R R and R beinghydrogen, and no more than three of R R R and R being aryl.

The novel synergistic combinations provide improved flame-retardanceover the additives of the prior art and, additionally, generally providethis superior result at lower concentrations than previously believed tobe necessary for most of the known additives. The results shown by theuse of the above-mentioned flame-retardant combinations are surprisingand unexpected in that the combinations provide a greater degree offlame-retardancy than one would expect from the results shown by the useof the components individually, i.e. they are synergistic.

Additionally, the effectiveness oi the combinations is achieved in theabsence of any third ingredient, such as antimony compounds orchlorinated hydrocarbons. This synergism moreover, does not appear to belimited to specific combinations, but is broadly applicable to anycombination of a compound represented by Formula I and a compoundrepresented by Formula II.

DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENTS Asmentioned above, the first critical component of my novelflame-retardant compositions is a compound represented by Formula I,above. These compounds are well known in the art, as are methods oftheir production, as represented by US. Pat. Nos. 3,152,172 and3,196,191 which patents are hereby incorporated herein by reference.

As disclosed in said references, the compounds of Formula I aregenerally prepared by first preparing the anhydride, wherein R and Rtogether are oxygen, by the reaction of hexachlorocyclopentadiene andcis-4-cyclohexene-l,2-dicarboxylic anhydride. The free dicarboxylic acidand the esters may then be prepared from the anhydride by conventionalmeans, i.e. reaction with an appropriate alcohol or substituted alcohol,e.g. phenol. Alternatively, the acid or esters may be prepared byreaction of the hexachlorocyclopentadiene and the diacid or diester ofsaid cis-4-cyclohexene-l,Z-dicarboxylic anhydride.

The anhydride represented by Formula I is a crystalline solid materialhaving a melting point of about 275 C The other compounds are alsosolids of high melting points. The compounds of Formula I may be used inconcentrations ranging from about 1.0% to about 20.0%, by weight, basedon the weight of the polymer to which they are added.

The second critical component of my novel flame-retardant compositionsis a monophosphonium halide represented by Formula II, above. Thesehalides may be produced by any known procedure, one of which isdisclosed in US. Pat. No. 3,005,013 which patent is hereby incorporatedherein by reference.

The monophosphonium halide may be incorporated into the polymericmaterial in concentrations ranging from about 1.0% to about 20.0%, byweight, based on the weight of the polymer to which it is added.

The term aryl radical, as used herein in regard to the substitutents R RR and R of Formula II, above, is meant to include not onlycarbon-hydrogen cyclic compounds but also lower alkyl and halogen andringsubstituted phenyl compounds and the scope of the instant inventionshould be construed so as to include compounds falling within thisdefinition.

The ratio of the compound represented by Formula I to the compoundrepresented by Formula II should range from about 3 to 1 to 1 to 3,respectively, in the polymer.

Any thermoplastic polymeric material may be rendered flame-retardant bythe incorporation therewith of the above-identified flame-retardantcombinations. Specifically, however, the vinyl type polymers, wherein amonomeric material is polymerized, by known methods, e.g. by use offree-radical generating actalysts, irradiation, anionic and cationiccatalysts, etc. are those preferred. Examples of the vinyl type polymerswhich may be used to form my novel compositions are the homopolymers andcopolymers of acrylamides and N-substituted acrylamides, polyvinylacetates, butadiene copolymers, e.g. acrylonitrile-butadiene-styrenecopolymers, the polymers of acrylonitrile, e.g. acrylonitrile styrenecopolymers, polyacrylonitrile etc.

Additionally and even more preferably, one may incorporate theflame-retardant synergistic combinations mentioned above into suchpolymers as the homopolymers and coploymers of styrene, i.e.polystyrene, 0&- methyl styrene polymers, styrene-acrylonitrilecopolymers, etc. the a-olefin polymers, such as the homopolymers andcopolymers, etc. containing, as the major constitutent thereof,ethylene, propylene, such as polyethylene, including high densitypolyethylene, polypropylene and the like and the acrylate andmethacrylate homopolymers produced from monomers having the formula IIICH2=CC It 0R wherein R is hydrogen or a methyl radical and R is an alkylradical having from 1 to 6 carbon atoms, inclusive. Examples of monomersrepresented by Formula III include methyl acrylate, ethyl acrylate,n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butylacrylate, isobutyl acrlate, n-amyl acrylate, t-amyl acrylate, hexylacrylate and their corresponding alkyl methacrylates, etc. andcopolymers thereof with one another and with minor amounts, i.e. notmore than about 10%, by Weight, of comonomers such as acrylonitrile,styrene, etc.

Also such polymers as the nylons, e.g. adipic acidhexamethylenediaminereaction products; the polycarbonates, i.e. phosgene-Bisphenol Areaction products; the so-called impact polymer, i.e. rubber-polymerblends such as blends of polystyrene with 540% of butadienestyrene, theABS type resins, e.g. blends of butadienestyrene andstyrene-acrylonitrile; blends of grafted polybutadiene etc. with hard,resinous po ymers such as terpolymers of methyl methacrylate, styreneand acrylonitrile etc., and flammable plasticized polymers such asplasticized polyvinylchloride, and the like may be made flame-retardantby the incorporation therein of the synergistic combinations discussedhereinabove.

The novel flame-retardant combinations claimed herein may be added tothe various polymers, as such, or as individual components, by any knownmethod. That is to say, the flame-retardant components may be added tothe polymer, as such, or in combination by (1) milling the polymer andthe components on, for example, a two-roll mill, in a Banbury mixer,etc. by (2) molding the components and the polymer simultaneously, by(3) extruding the polymer and components or by (4) merely blending allthe materials together in powder or liquid form and thereafter formingthe desired ultimate product. Additionally, the flame-retardantcomponents or combination may be added during the production of thepolymer, i.e. during the monomer polymerization, provided, however, thatthe catalyst, etc. other conditions and other ingredients of thepolymerization system are inert thereto.

It is also within the scope of the instant invention to incorporate suchingredients as plasticizers, dyes, pigments, heat and light stabilizers,antioxidants, antistatic agents, photochromic materials and the likeinto the flame-rearded polymer compositions claimed herein.

The following examples are set forth for purposes of illustration onlyand are not to be construed as limitations on the present inventionexcept. as set forth in the appended claims. All parts and percentagesare by weight unless otherwise specified.

METHOD OF TESTING Any appropriate flame-retardance test may be used todetermine the flame-retardant properties of any specific combination ofcompounds represented by Formulae I and II, above. One test I have foundto be reasonably efficient is a modified version of that test identifiedas ASTM D-635-56T. The specifications for this test are: a cylindricalextrudate 68" in length, 0.045 in diameter is prepared using a meltindex apparatus (ASTM D-1238-627), marked at the 1" and 5" lengths andthen supported with its longitudinal axis horizontal. A Bunsen burnerwith a 1" blue flame is placed under the free end of the strip and isadjusted so that the flame tip is put in contact with the strip endnearest the 5" marking. At the end of 30 seconds, the flame is removedand the specimen is allowed to burn. If the specimen does not continueto burn after the first ignition, it is immediately recontacted with theburner for another 30 seconds. If, after the two burnings, the strip isnot burned to the .5" mark, the specimen is designated as non-burning.If the specimen has burned to the 5" mark but not to the 1 mark it isdesignated as self-extinguishing.

Example 1 To parts of polypropylene are added 5 parts of methyltriphenyl phosphonium bromide and 5 parts of 2,3dicarboxy-5,8-endomethylene-5,6,7,8,9,9-hexachloro-1,2,3,4,4a,5,8,8a-octahydronaphthalene anhydride (hereinafter sometimescalled DEMON). The resultant mixture is placed in a suitable blender anddry-blended for 4 hours. The blended product is then transferred to amelt-index apparatus which is preheated to 250 C. Following one minuteof aging, a 2.2 kg. weight is placed on the plunger and an extrudate of6-8 inches in length is obtained. This sepcimen is marked and testedaccording to the above enumaterated flame-retardance test. The resultsare set forth in Table 1, below.

Various other flame-retardant combinations are then incorporated intovarious other resins according to Example l and comparisons are madebetween the resultant compositions and control compositions. Theseresults are also set forth in Table 1, below.

Q 1.11%.... cm 202mm 1 625m 1 mm 5 w 0c 1 3 1.11% x 0 0m 1811. 9mm hm-JEGQQQQKY E 8:v m E E@oo u mw m -1 ZEHQ mm 1 .1 1 m .5 6s ow cm 1on1. 5

Q -1 1. E 3 ZOEHQ .1 1.11%

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m 1...-..ot 3% w w 5m m 33% 423A 33% :562 wm m w 3. w w 5 um 32am Eno.axoao& 3Qo.5hxo9.o& raoahuonbwo m 6m Q 1. w w m c 6w w w w 3 mm TS Q1.1111111QEDM A 0 am w 6 1.1.. n 3 1.11.110? w 10 m m 1-0. 1 n w mm202mm n m E 1... 523 1.....1wm 28m 3 n 6 3v S n 5 33M 33 4 553 AE B EEQNmm m m c 2w 1. w w mm m .5 Efi o=o m 456mm 528mm 1 -3525 1 m 3 d w m w 52 r fim 4 5 0m 2 MO w w 6 3 2 1. EE A Q E EhN 2 c4 -11... 0w 0w D o d bw 1 A $w 3 3 Q w 1- 0w 1 1ou11.

2 m w 1 1.114% m 13 0 D m v 1. w w w 2 m m 1.11ow w w 2 Q n 5 5 m -35m 5m 5 m 2 0 3 m w m n w d 0 m 35:296 m 3 2v w Q2 5 m u 2 m h 4 .5 m 3:cg9w E 3$:m& 12 226 2 m 1on1. 0w w w m o m .5 wonm u m 1 EH am 13am1-1.111. 111111-111...1.1.. w m h v 1 2 m m 3 1 6 w a 63 dszaoafiom 9m202mm 9m .5 1325 35am 35am fi m 3 M m BSZ Q ZOEHQ 2 m N E E 2 NM 28 m 0m is ozmmos H HA Q TABLE I-Continued R X Percent DEMON Derivative2-eyan0ethy1 2-cyanoethyl 2-cyanoethyl Br .do. d0.. ....do BrPhosphonium Halide All of the products produced according to Examples 1to 74 exhibited excellent flame-retardant, as indicated fifigj fitherein, and, additionally, each and every system exhibited g 1 littleor no color change when subjected to high tem- 5 i i i i i E 5 peratureprocessing conditions.

Iclaim: f i E ii i i 1. A flame-retardant composition comprising a com-5 3 E Ej E i bination of (1) a compound having the formula 5 E 5 2: 5 1H1 I 5 E i i :8 1 10 1 5 58 i :3 I '2 I E E E3 I 01 i i 1 is 5E o1 o r rcnz 0 IQ IH 1 y E :5: I 1O 0 o CH-G-R :fil 0012] :g as i C\l/(|J\ HO-REE iiE E 01 o H CH2 -35as-3 1 i ii 5 E as lag E g g wherein R and Rtaken together, form an oxygen 5 i E E E atom and R and R takenseparately, are an alkoxy radical E 1' E E 3 of 18 carbon atoms,inclusive, a haloalkyl radical of 1-4 5 i S i 5 carbon atoms, inclusive,or a hydroxy radical, and (2) i i i E j a monophosphonium halide having.the formula 5 E l E R5 R2 E f x- I I 1 l R4 R3 333 wherein R R R and Rare, individually, hydrogen, an alkyl radical of l-8 carbon atoms,inclusive, a cyano, hydroxy or carboxy substituted al'kyl radical of 1-4carbon atoms, inclusive, an allyl radical, an aryl radical of 61()carbon atoms, inclusive, an aralkyl radical of 7-11 carbon atoms,inclusive, a halo or polyhalo ar-substituted aralkyl radical of 7-11carbon atoms, inclusive, or a carboalkoxyalkyl radical of 36 carbonatoms inclusive, no more than one of R R R and R being hydrogen and Xrepresents chlorine or bromine and no more than three of R R R and Rbeing aryl the ratio of compound (l) to compound (2) range from 3 to 1to 1 to 3.

2. A flame-retardant composition according to claim 1 wherein (2) ismethyltriphenyl phosphonium bromide. 3. A flame-retardant compositionaccording to claim 1 wherein (2) is tetra(Z-cyanoethyl)phosphoniumbromide.

4. A flame-retardant composition according to claim 1 wherein (2) is2-cyanoethyl triphenyl phosphonium bromide.

5. A flame-retardant composition according to claim 1 wherein R and Rtogether form an oxygen atom.

6. A flame-retarded composition comprising a theromoplastic polymerselected from the group consisting of polymers of unsaturated monomers,polycarbonates and polyamides having incorporated therein aflame-retarding amount of the composition of claim 1, the amount of eachcompound in the combination being less than that 5 amount at which thecomponent individually functions similar to the combination.

7. A flame-retarded composition according to claim 6 wherein saidthermoplastic polymer is polypropylene.

8. A flame-retarded composition according to claim 6 wherein (Z) istetra(2-cyanoethyl)phosphonium bromide and R and R together form anoxygen atom.

9. A flame-retarded composition according to claim 6 wherein saidthermoplastic polymer is polypropylene, (2) istetra(2-cyanoethyl)phosphonium bromide and R and R together form anoxygen atom.

I I I I I I I v 1 l I I I I v I I I I I l l I I I I I I I I I I I l I lI l I I I I I Adipic acid-hexamethylenediamine reaction product;

10. A flame-retarded composition according to claim 3,442,980 5/1969Grabowski 26045.75 6 wherein (2) is tetra (2-cyan0ethyl)phosphonium bro-3,446,822 5/ 1969 Dun'kel 260-346.6 mide.

References Cited HOSEA TAYLOR, Primary Examiner UNITED STATES PATENTS 5US CL 3,152,172 10/1964 Roberts et a1 260--468 3,422,047 1/1969Cannelongo 260-285 252-81 52604535 45'95 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 1530 089 Dated September 22 192;)

Inventor(s) Christos Savides It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Claim 1, line 26, the term "haloalkyl" should be haloalkoxy uimifi MD85153 JAN 5 1971 m I. m. B- Mng 0mm Oomiuaiom of hunts FORM Po-105O(IO-691 uscoMM-oc scan-Pu U3. GDVIIIIIII" "IRVING OFFICE I"! 0-8il-3l4

